Patient repositioning device and method

ABSTRACT

Patient repositioning device ( 10 ) comprising, a patient supporting panel ( 20 ), at least one pair of laterally adjustable side support structures ( 30   a,b,    40   a,b ) for sideways supporting a patient ( 50 ) on the supporting panel ( 20 ). To achieve repeatable repositioning of a patient body ( 50 ) each pair of side support structures ( 30   a,b,    40   a,b ) are linked by a link arrangement ensuring that the side support structures ( 30   a, b,    40   a, b ) automatically are centered about a longitudinal axis (A-A) of the supporting panel ( 20 ) indicating the centre of a patient ( 50 ) supported on the panel ( 20 ). There is also provided a method of repositioning a patient.

The present invention relates to a patient repositioning deviceaccording to the preamble of claim 1 and a method of repositioning of apatient on a treatment or diagnostic table for radiological proceduresaccording to the preamble of claim 17.

BACKGROUND OF THE INVENTION

In radiotherapy as well as in surgical operations, the possibility oflocating the actual disease volume with great accuracy is essential forthe success of the treatment. To minimize the risk for geographical missin the treatment, the correct target volume in the body is identified indiagnostic devices such as X-ray systems, Computerized Tomographydevices (CT), Gamma Cameras, Nuclear Magnetic Resonance units (NMR orjust MR). The responsible physician specifies the target volume to betreated by contours in the diagnostic images and these images are thenused for planning of the treatment by manual or computerized methods.The therapeutic procedure, Radiation Therapy or Surgery, is thenperformed according to the treatment plan. Since the target volumeusually is located deep inside the patient body, it is essential thatthe patient, and especially the target volume, can be repositioned toexactly the same coordinate system as during the diagnostic procedure.This is particularly important in Radiation Therapy of cancer where theintended tumor dose is given as repeated small daily radiation dosesduring several weeks. It is thus important that in each treatmentsession the tumor in the patient is correctly positioned relative to theradiation field of the radiotherapy apparatus. Repositioning of patientsis also important in diagnostic procedures, particularly when differentimaging modalities are used and the images are superimposed to obtainmore diagnostic information about the patient.

One prevalent method for positioning a patient's body is that the skinof the part of the body that is to be subjected to radiotherapy ismarked with a felt-tip pen, with or without supplementary tattoo points.By means of skin marks and laser position beams in the treatment room,the therapist tries to align the patient in the correct position on theradiotherapy table for each treatment session. The drawback of thismethod is that the skin is elastic and can move fairly much relative tothe skeleton and the target volume. This movement of the skin and theskin marks in relation to the target volume makes it necessary to usewide safety margins on the radiation fields to ensure that the tumor isnot outside the radiation field during any of the treatment sessions.The increased size of the radiation fields result in that large volumesof normal tissue without cancer become unnecessarily irradiated. Thiscauses higher doses of radiation energy to the body and leads to ahigher risk for undesired side-effects of the radiotherapy. Byirradiating greater volumes than necessary, the total radiation dosecannot be increased to the desired level for good curative effect incertain areas, e. g. close to critical organs or tissue with highsensitivity to radiation. A higher accuracy in repositioning of thepatient, both during the diagnostic procedure and the treatment, allowsa reduction of the safety margin due to position uncertainty and thatgives less dose to the healthy tissue and allows a higher dose to thetarget volume if desired. This in turn gives less risk for side effectsand a higher probability for a successful treatment.

A plurality of equipment and techniques are currently available toreduce the deviations in the positioning of a patient, so-calledfixation devices such as masks, bite blocks, straps, plastic shells etc.The fixation devices should be usable both with the diagnostic devices,the therapy simulator and the therapy machines with negligible influenceto the radiation. The problem with this kind of fixation devices is thatthe patient who lies down in a shell or is pulled on a horizontaltreatment table to get into a table-mounted mask will stretch the skindifferently each time, which results in that the skin marks don't keeptheir position in relation to the target volume. More complex fixationsdevices with masks that are custom made for each individual patient givea better lateral repositioning, but due to the essentially cylindricalshape of the human body they still permit a fair bit of rotationmovement inside the mask, which limits their accuracy. Custom made masksalso require significant storage space and systems for safe and certainidentification to guarantee that every patient gets the right mask everytime.

One device that overcomes some of these problems is disclosed in U.S.Pat. No. 5,983,424. The proposed device is comprised of a non-yielding,upright panel element, a tilting and conveying assembly being arrangedat the end of the table for tilting the panel element together with thepatient from the upright orientation to a lying orientation andconveying these to a defined place on the table.

The design and function of said device is based on the knowledge thatthe skin is affected by gravity as the position of the body changes. Thethicker the subcutaneous fat, the greater the movements. Also thepatient's movement of hips and other parts of the body is difficult toreproduce by today's techniques.

The positioning is thereby performed by carrying out the settings whenthe patient is placed in an upright position. When a person is standingwithout clothes and shoes, the skin costume will have a well-definedposition in relation to the skeleton. The legs have a given length andthe hip-joints will have a position relative to the floor surface thatis the same each time. The skin will be stretched due to gravity, butthe stretching will be the same for each session during the radiotherapyperiod, unless an extreme loss of weight takes place.

The patient stands on a base plate whose rear part is connected to anupright panel behind the patient's back. When the patient takes hisnatural upright position for the first time, the skin is marked in asuitable position of the body by means of laser position lights or someother technique connected to the panel and indicating a relationshipbetween the back panel and the body. The relationship of the body to thepanel then determines the positioning each time.

Various fixation means are then attached to the panel, which likebuilding bricks are snapped onto the panel at various levels, they canbe removed after positioning or remain on during diagnostic procedures,simulation work or during radiotherapy. These may involve positioningmarks, lateral supports, supports for the curve of the back, head-neck,straps, masks and other fixation aids, connected to the panel.

However, the above procedure of laser positioning of a patient relativeto the panel is rather complex and time consuming and the same appliesto the attachment of various fixation means to the panel to assureidentical repositioning for each treatment in a treatment cycle.Furthermore a complex description of the position of each of the variousmeans attached to the panel is needed to rebuild the supportingarrangement for a special patient, unless the whole panel with thesupporting arrangement can be stored in between the treatment sessions,but this requires a large number of repositioning panels at eachtreatment site, which is expensive and requires a storage system andspace for unused panels. If the different support structures instead areindividualized or produced in a large number of sizes and differentshapes, these support structures have to be stored and handled in anefficient way.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a new patientrepositioning device and a method for repositioning of a patient, thatovercomes one or more drawbacks of the prior art. This is achieved bythe repositioning device as defined in claim 1 and the method accordingto claim 17.

One advantage with such a device and method is that the procedure ofrepositioning a patient on a repositioning device is vastly simplified,as the device always centers the patient along the same axis relative tothe device.

Another advantage is that one and the same repositioning device can beused for repositioning essentially all patients within a large range oflength and width without time consuming adaptations of different supportstructures.

Still another advantage of this device and method is that essentially noadditional support structures of different shapes and sizes are needed,which alleviates both the need for storage space as well as the need foran identification system to ensure that the right type and arrangementof fixation parts is used for each patient.

Embodiments of the invention are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail below with reference to thedrawings, in which:

FIG. 1 is a schematic view of one embodiment of the present invention.

FIG. 2 is another schematic view of one embodiment of the presentinvention similar to FIG. 1 illustrating some alternative supportarrangements.

FIG. 3 is a schematic cross-sectional view of one possible linkarrangement along B-B in FIG. 1.

FIG. 4 is a schematic view of another link arrangement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 schematically shows one embodiment of the patient repositioningdevice 10 according to the present invention. As discussed above,repositioning devices 10 of tilting type presents a large number ofadvantages compared to other prior art repositioning devices, but theknown devices of tilting type tend to be complicated to use.

Like the device disclosed in U.S. Pat. No. 5,983,424, the repositioningdevice 10 according the present invention comprises a patient supportingpanel 20 and at least one pair of laterally (along the broken lines B-Band C-C respectively) adjustable side support structures 30 a,b, 40 a,bfor sideways supporting a patient 50 on the supporting panel 20. But inorder to achieve quick and reliable centering of the patient 50 relativethe panel 20, each pair of side support structures 30 a,b, 40 a,b arelinked by a link arrangement, which is described below, so that theyautomatically are centered about a longitudinal axis A-A of thesupporting panel indicating the centre of a patient 50 supported on thepanel 20.

To achieve reproducible centering of patients 50 each pair of laterallyadjustable side support structures 30 a,b, 40 a,b are arranged tosupport the patient 50 at a body region with bone structures close tothe skin surface, such as the hip region and the chest region. By thisgeneral arrangement of the side support structures 30 a,b, 40 a,b themajority of all patients can be centered on the device with sufficientaccuracy for the following diagnostic and treatment procedures.

The embodiment shown in FIG. 1 comprises two pairs of side supportstructures 30 a,b and 40 a,b, a first pair 30 a,b (hip support) arrangedto support the patient 50 at the hip region 60 and a second pair 40 a,b(chest support) arranged to support the patient 50 at the chest region70. In order to conform with a larger number of patients with respect totheir height at least one of the pairs of side support structures 30a,b, 40 a,b, preferably both, are longitudinally adjustable, as isindicated for the chest support 40 a,b in FIG. 2. The chest support 40a,b is mounted on a longitudinally moveable mounting base 80, which ismoveable between the positions indicated by D and E in FIG. 2.Preferably the mounting base 80 is moveable between a number of fixedpositions, so that the base 80 can be arranged in the same position eachtime a patient is to be treated.

Depending on the type of diagnostic or treatment equipment that therepositioning device 10 is to be used in the device may be comprised ofany suitable material. But as the main area of use is radiodiagnostic orradiotherapy essentially all parts located in the upper section of therepositioning device preferably are made of a radiolucent material.However, parts located in regions that do not disturb the diagnosticimaging or treatment may be allowed to be non-radiolucent. One way toavoid having obstructing elements that cannot be made in radiolucentmaterial in the upper section is to arrange such elements outside thissection e.g. in or below the feet region. Such obstructing elements aremainly associated with the link arrangement for the support structures30 a,b, 40 a,b and will be discussed in greater detail below.

FIG. 3 shows a cross sectional view of the repositioning device 10 witha link arrangement comprising a double-threaded screw 90 to achieve thelinked centered behavior of the support structures 30 a,b. Thedouble-threaded screw 90 is driven for rotation by a drive motor 100 andthe support structures 30 a,b are arranged to move apart or together ina synchronized centered manner by threaded portions 110 a,b depending onthe direction of rotation. There are obviously a number of modificationsand variations that may give the same result of a centered motion of thesupport structures 30 a,b, 40 a,b, such as two threaded screws rotatingin opposite directions through gears or the like. Further, the drivemotor 100 can be arranged e.g. at the foot end of the repositioningdevice 10 and drive the double-threaded screw 90 by a longitudinal axisand an angle gear, whereby the amount of non-radiolucent material can bearranged outside the treatment section of the repositioning device 10.The link arrangement can also be made with two separate motors, each onecontrolling the position of one side support, and with the motorselectronically linked to synchronize their motions to obtain thecentered motion of the supports.

FIG. 4 schematically shows another type of link arrangement for therepositioning device 10 according to the present invention wherein thesupport structures 30 a,b are linked by a mechanical lever system 120.The resulting movement of the support structures 30 a,b linked by such alever system is indicated by the line B-B in FIG. 2. The mechanicallever system 120 is arranged such that only levers 130 a,b extends intothe treatment section of the repositioning device 10, thereby minimizingthe amount of non-radiolucent material in the treatment section. As canbe seen in FIG. 4 all other parts of the mechanical lever system 120 arearranged at the foot end of the repositioning device 10. The levers 130a,b are pivotally supported at pivotal points 140 a,b respectively andare centered and linked together by link levers 150 a,b. The link levers150 a,b are pivotally joined by a centering and locking mechanism 160,comprised of a slider 170 and a shaft 180. The centering and lockingmechanism 160 ensures that the levers 130 a,b always are mutuallycentered through the link levers 150 a,b respectively, and preferablyprovides one-way automatic lock system that in normal state locksoutward movement of the support structures while allowing inwardmovement to locate a patient. The locking mechanism 160 is preferablyreleased by a release button or the like (not shown). Alternatively, themechanical lever system 120 may be controlled by a drive motor arrangedto drive the shaft 180 for rotation, whereby the shaft 180 and theslider 170 are provided with threads.

In the discussed embodiments the repositioning device 10 has been shownwith two pairs of support structures 30 a,b, 40 a,b, however it maycomprise any suitable number of pairs. In one embodiment there isprovided a head support in the form of a pair of support structures(head support). To assure that the head is not tilted when it is fixedby the head support, each support may be provided with a sight structurethat allows aligning of respective skin markings on the head of thepatient. Moreover, additional support may, if needed, be supplied bysupplement supports of more conventional type, and the supportstructures may, if needed, be fitted with support elements of differentshape and or size to achieve a close fit for different patients.

The patient supporting panel or any of the support structures may alsohave alignment means such as reference marks, laser lines or othersimilar means, to aid in rotational adjustment of the patient againstskin marks in different body regions.

The panel 20 of the repositioning device 10 may in conventional ways befitted with or be fittable with supplementary aids such as visualgraduated scales or markers that are visible in diagnostic images tomake it possible to position the panel by its own reference coordinatesystem in relation to equipment in a diagnostic clinic and radiotherapyclinic.

The panel can also be fitted with electronic components such astransceivers, magnets, light sources etc. which can indicate theposition in relation to the room and equipment of different types, theposition of the patient, the position of the radiation fields on thepatient and against the panel or the means of the panel.

Further it is possible to use more than one panel 20 in one treatmentsession by one panel being arranged behind the patient and one panel(not shown in figures) with accessories being mounted in front of thepatient in connection with radiotherapy.

What has been said about the panel 20 does not necessarily signify aflat panel. It can also be shaped like a bucket seat, adapted completelyto the contour of the patient, or it may have any appearance whatsoeverand it may also be integrated into the treatment table of the diagnosticor therapeutic device.

The support structures may stay on the device to hold the patient inplace during the whole procedure and serve as patient fixation, but theymay also be removable after the positioning process to allow other meansof fixation during the diagnostic or treatment procedure. To furtherassure that the patient body gets a consistent setup each time, one orseveral of the side support structures may be provided with a pressuresensor that registers the pressure that the support structure applies onthe patient.

Furthermore for easy adjustment of the patient to the intended position,the patient supporting panel can be provided with a low-friction surfaceor movable panels that lower the friction between the patient body andthe patient supporting panel, so that friction cannot cause distortedpositioning.

Although the present invention is described in the form of a patientrepositioning device of tilting type, the linked patient supportingpanels according to the invention may be used for all types of patientrepositioning devices where a repeatable positioning of a patient bodyis desired. For patient repositioning devices of essentially horizontalnon tilting type, the patient supporting panel is preferably providedwith low-friction surface or movable panels as discussed above.

There is also provided a method of repositioning a patient using arepositioning device 10 according to the present invention. The methodcomprises the steps:

-   -   arranging the patient with the back, side or front against a        patient supporting panel of a patient repositioning device 10,    -   sideways repositioning the patient on the supporting panel using        at least one pair of laterally adjustable side support        structures, the side support structures being linked so that        they automatically are centered about a longitudinal axis of the        supporting panel ensuring that the patient is essentially        identically repositioned about said longitudinal axis every        time.

When the repositioning device 10 is provided with longitudinaladjustable support structures the method prior to the step of sidewaysrepositioning compromises the additional step of:

-   -   adjusting the longitudinal position of each pair of side support        structures according to individually selected parameters.

When the patient supporting panel or side support structures 30 a,b, 40a,b, are provided with alignment means to aid in rotational adjustmentof the patient against skin marks in different body regions the methodcompromises the additional step of:

-   -   adjusting the patient rotation by lining up skin marks with the        alignment means.

When patient repositioning device is of tilting type the patient isarranged on the patient supporting panel in an upright position and themethod comprises a last step of:

-   -   tilting the patient supporting panel to a predetermined        position.

1. Patient repositioning device (10) comprising: a patient supportingpanel (20); at least one pair of laterally adjustable side supportstructures (30 a, b, 40 a, b) for sideways supporting a patient (50) onthe supporting panel (20) characterized in that each pair of sidesupport structures (30 a, b, 40 a, b) are linked by a link arrangementensuring that the side support structures (30 a, b, 40 a, b)automatically are centered about a longitudinal axis (A-A) of thesupporting panel (20) indicating the centre of a patient (50) supportedon the panel (20).
 2. Patient repositioning device (10) according toclaim 1 characterized in that each pair of laterally adjustable sidesupport structures (30 a, b, 40 a, b) are arranged to support thepatient (50) at a body region with bone structures close to the skinsurface, such as the hip region (60), the chest region (70) and thehead.
 3. Patient repositioning device (10) according to claim 1characterized in that it comprises a first pair of side supportstructures (30 a, b) arranged to support the patient (50) at the hipregion (60) and a second pair of side support structures (40 a, b)arranged to support the patient (50) at the chest region (70). 4.Patient repositioning device (10) according to claim 1 characterized inthat at least one pair of side support structures (30 a, b, 40 a, b) arelongitudinally adjustable.
 5. Patient repositioning device (10)according to claim 1 characterized in that essentially all parts locatedin the treatment section of the repositioning device are radiolucent. 6.Patient repositioning device (10) according to claim 1 characterized inthat the link arrangement comprises a one-way automatic lock system. 7.Patient repositioning device (10) according to claim 1 characterized inthat the link arrangement comprises a drive motor (100).
 8. Patientrepositioning device (10) according to claim 1 characterized in that thelink arrangement comprises a double-threaded screw (90).
 9. Patientrepositioning device (10) according to claim 1 characterized in that thelink arrangement is comprised of two electronically linked drive motors.10. Patient repositioning device (10) according to claim 1 characterizedin that the link arrangement comprises a mechanical lever system (120).11. Patient repositioning device (10) according to claim 1 characterizedin that the link arrangement comprises at least one non radiolucent partthat is arranged outside of the treatment section of the repositioningdevice, e. g. below the feet support.
 12. Patient repositioning device(10) according to claim 1 characterized in that the patient supportingpanel and/or one or several of the side support structures (30 a, b, 40a, b) are provided with alignment means for adjusting the rotationalposition of the patient.
 13. Patient repositioning device (10) accordingto claim 1 characterized in that the patient supporting panel (20) isprovided with a low-friction surface or movable panels for easyadjustment of the patient (50) to the intended position.
 14. Patientrepositioning device (10) according to claim 1 characterized in that oneor several of the side support structures (30 a, b, 40 a, b) can beremoved from the patient supporting panel (20) after the alignmentprocedure.
 15. Patient repositioning device (10) according to claim 1characterized in that at least one of the side support structures (30 a,b, 40 a, b) is provided with a pressure sensor.
 16. Patientrepositioning device (10) according to claim 1 characterized in that itis of tilting type.
 17. Method of repositioning a patient (50)comprising the steps: arranging the patient (50) with the back, side orfront side against a patient supporting panel (20) of a patientrepositioning device (10), sideways repositioning the patient on thesupporting panel (20) using at least one pair of laterally adjustableside support structures (30 a, b, 40 a, b) characterized in that theside support structures (30 a, b, 40 a, b) are linked so that theyautomatically are centered about a longitudinal axis (A-A) of thesupporting panel (20) ensuring that the patient (50) is essentiallyidentically repositioned about said longitudinal axis (A-A) every time.18. Method according to claim 17 characterized in that it prior to thestep of sideways repositioning comprises the step of: adjusting thelongitudinal position of each pair of side support structures (30 a, b,40 a, b) according to individually selected parameters.
 19. Methodaccording to claim 17 characterized in that it also comprises the stepof: adjusting the rotational position of the patient (50) usingrotational alignment means.
 20. Method according to claim 17, whereinthe patient repositioning device is of tilting type characterized inthat the patient (50) is arranged on the patient supporting panel (20)in an upright position and the method comprises a last step of: tiltingthe patient supporting panel (20) to a predetermined position.